CDM-Based Two-Degree-of-Freedom PID Controller Tuning Rules for Unstable FOPTD Processes

  • Somasundaram SEmail author
  • Benjanarasuth T
Conference paper


This paper deals with the coefficient diagram method (CDM)-based two-degree-of-freedom proportional integral derivative (CDM-PID) controller tuning rules for unstable first-order plus time delay (UFOPTD) processes. The explicit tuning rules for setting the PID controller parameters are derived using a general UFOPTD transfer function model, the second-order Taylor denominator approximation technique and the pole allocation strategy named CDM. The derived tuning rules are novel, directly relating the controller parameters to the process model parameters. Simulation results indicate that the CDM-PID controller with the proposed tuning rules deliver better performance than other available PID controller tuning methods.


CDM PID 2DOF UFOPTD Tuning rules 



coefficient diagram method


proportional integral derivative




unstable first-order plus time delay


equivalent time constant


stability indices


settling time


process gain


process time constant


process time delay


proportional gain


integral time


derivative time


percentage overshoot


sum of the total variation


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© Springer Nature Switzerland AG 2020

Authors and Affiliations

  1. 1.Department of Electronics & Instrumentation EngineeringAnnamalai UniversityChidambaramIndia
  2. 2.Faculty of EngineeringKing Mongkut’s Institute of Technology LadkrabangBangkokThailand

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